Slide rule



Sept. 1, 1953 P. J. ToiEN 2,650,762

SLIDE RULE Fi1ed April 9, 1951 3 sheets-Sheet 1 /0/ 5:5/ voz FW@ f/s Sept. 1, 1953 P. J. 'rolEN 2,650,762

SLIDE RULE Filed April 9, 1951 3 Sheets-Sheet 2 P. J. Ton-:YNF 2,650,762

SLIDE RULE Sept. 1, 1953 Filed April 9, 1951 5 Sheets-Sheet 3 Patented Sept. 1, 1953 UNITED STATES PATENT OFFICE SLIDE RULE Paul J. Toien, Los Angeles, Calif.

Application April 9, 1951, Serial No. 219,974

10 Claims. (Cl. 23S-79.5)

This invention relates to slide rules and more particularly to a slide rule which includes a plurality of differentially actuable members energiaable by a motor associated therewith.

Conventional slide rules are usually of the slipstick construction wherein the -base member, having a central longitudinal groove therein, is provided with an elongated reciprocable member mounted in said groove, said base and said reciprocable member being longitudinally snif-table with respect to each other to permit calculations to be made by the utilization of the rule. Among the inherent disadvantages of such conventional construction is the fact that the use of a conventional slide rule necessitates the use of both hands so that it is not possible to simultaneously make and write down the calculations with the use of the conventional rule.

The conventional dial type rule slide rule Wherein one at disc is superimposed above the other,

said discs being of decreasing diameters, also necessitates the use of two hands.

It is, therefore, a primary object of my invention to provide a slide rule which can be manipulated by the use of one hand and which thus permits the user thereof to make notes of his calculations while actuating the slide rule.

An additional object of my invention is the provision of a slide rule which is constituted by a plurality of differentially actuable members energizable by a motor associated therewith, the differential actuation of the plurality of mea bers being controllable by rst control means which is adapted to energize the plurality of members simultaneously and a second control means which is adapted to cause the differential actuation of at least one of said members with respect to others of said members.

Another object of my invention is the provision of a slide rule which includes a plurality of superimposed, difierentially actuable members having provided on the peripheral portions thereof conventional slide rule scales, said members being housed in a housing which has a viewingr Window therein and being energizable by a motor associated therewith and mounted in said housing.

A further object of my invention is the provision of a slide rule of the aforementioned type which includes a plurality of substantially cylindrical members having scales mounted upon the peripheral portions thereof, the slide rule incorporating a motor which has associated therewith a primary drive and a plurality of secondary drives, said secondary drives being simultaneously or differentially actuable to cause the simuliii taneous or differential movement of the members with which they are associated.

An additional object of my invention is the provision of a slide rule of the aforementioned type which includes a plurality of juxtaposed, rotatable scales, said scales having associated therewith a primary drive and a plurality of secondary drives, said secondary drives being simultaneously or differentially actuable to cause the simultaneous or differential actuation of said scales, at least one of said scales being continually and operatively connected to a motor constituting the source of energy for said slide rule.

Another object of my invention is the provision of a slide rule of the aforementioned type in which the diierential energization yof the scales is accomplished by the provision of brake Ameans associated with at least one of the secondary drives so that the energization of said secondary drive can be prevented while others of said secondary drives are energized.

A further object of my invention is the provision of a slide rule of the aforementioned type in which some of the secondary drives are connected to the primary drive by clutch means, said clutch means being engageable with said primary drive to accomplish the simultaneous energization of all of said drives to permit the concomitant rotation of all of the scales associated with said secondary drives.

One of the inherent disadvantages of the conventional slide rule is the fact that such slide rules are not immediately available for use since they must be kept in the pocket or on the desk of the user and are frequently subject to being mislaid.

It is an additional object of my invention to provide a slide rule which includes a primary housing adapted to be disposed at a remote point upon the desk of the user of the slide rule where it can be readily viewed by the user and where it is immediately available for use.

A further object of my invention is the provision of a slide rule of the aforementioned type which, while it is positioned at a point remote from the user, includes a second housing having `embodied therein control means adapted to permit the remote actuation and control of the slide rule.

A further object of my invention is the provision of a slide rule of the aforementioned type which includes first control means adapted to cause the concomitant energization of the scales mounted in the primary housing, said nrst control .being adapted to cause the movement of the scaies in opposite directions at the will or the user of the slide rule.

An additional object of my invention is the provision of a slide rule of the aforementioned type which includes a second control adapted to cause the differential actuation of the scales of the slide rule so that one or more of the scales can be restrained from movement during movement of others of the scales.

Another object of my invention is the provision of a slide rule which is relatively simple to manufacture, includes a minimum number of component parts and can be readily maintained and repaired.

Other objects and advantages of my invention will be apparent from the following speciication and the accompanying drawings, which are for the purpose of illustration only, and in which:

Fig. 1 is a perspective view of a slide rule constructed in accordance with my invention;

Fig. 2 is a vertical, sectional view taken on the broken line 2--2 of Fig. 1;

Fig. 3 is an enlarged, fragmentary view of the primary drive and portions of the secondary drives which constitute a portion of the slide rule of my invention;

Fig. 4 is a transverse, partly sectional view taken on the broken line 4 4 of Fig. 2;

Fig. 5 is a circuit diagram showing the organization of the electrical components of my invention;

Fig. 6 is an enlarged, transverse, partly sectional view taken on the broken line 6-6 of Fig. 1; and

Figs. 7 and 8 are graphic representations of typical scales showing the manner in which a simple calculation may be made by the utilization of the slide rule of my invention.

Referring to the drawings and, more particularly, to Fig. 1 thereof, show a slide rule I0 constructed in accordance with my invention and including a first, remotely positioned, scale containing housing I2 and a second, control housing I3. Although my invention is described as embodied in first and second housings I2 and I3, respectively, so that the remotely positioned; housing I2 and the contents thereof may be controlled from the control housing I3 juxtaposed to the user of the slide rule It, it is conceivable that the controls, to be described in greater detail below, embodied in the control housing I3 be installed in the first housing I2, if the necessity therefor should arise. However, it is an important feature of my invention that the first housing I2 and the mechanism embodied therein are adapted to be positioned at a point remote from the user of the device and to be controllable from the relatively small control housing I3.

The rst housing I2 is substantially cylindrical in configuration and includes a side wall I5 provided with a viewing opening I6. Supported across the viewing opening I5 is a window I8 formed of glass, plastic, or similar material and having medially disposed thereupon a reference line I9. Although the reference line I9 is shown as borne upon the window I8, it is conceivable that equivalent points of reference be provided upon the housing proper adjacent the viewing opening I8 and it is not intended that the invention be limited to the specific type of reference line shown. `Mounted upon the side wall i5 and positioned at opposite ends of the viewing opening I6 are ver-tical panels 22 which bear upon their front surfaces indicia adapted to designate the various scales, to be described in part below, which constitute a portion of the slide rule of my invention.

The wall I5 of the rst housing if, as best shown in Fig. 2 of the drawings, defines a chamber 23 which is substantially bisected by a transverse intermediate partition 24 and which is adapted to receive in its lower portion an enclosure 25 whose upper wall 25 provides a mounting plate for various elements of the slide rule mechanism, in a manner which will be described in greater detail below. Supported upon the upper wall 25 of the enclosure 25 are an electric motor and reduction gear 28 which constitute the source of power for the slide rule I0 and which are operatively connected by means of a primary drive lindicated generally at 29 to a plurality of secondary drives indicated generally at 30.

Incorporated in and constituting a portion of the primary drive 29 is a reduction gear shaft 3i associated with the motor 28 upon the upper end of which is mounted a pulley 33. Positioned adjacent the motor 28 is a primary drive shaft 35, said drive shaft having its upper end supported in a bearing 3I in the intermediate partition 24 and its lower end supported in a bearing 38 in the upper wall 26 of the enclosure 25. Fixed upon the primary drive shaft 55 adjacent the upper end thereof is a pulley .d5 upon which is entrained a belt 4I which connects it to the pulley 33 on the shaft 3l to establish a driving connection between the motor 28 and the primary drive shaft 35.y Thus, when the motor 2.8 is energized, in a manner to be described in greater detail below, the rotation of the shaft 3i is accompanied by concomitant and equal rotation of the primary drive shaft 35. Fastened on the primary drive shaft 35 immediately below the pulley 40 is a first pinion 43, said pinion being rotatable by the primary drive shaft concomitantly with the rotation of the pulley t5. The pulley 40 and the pinion d3 are fixed against rotation with respect to the primary drive shaft 35 by means of set screws 44, or similar fasteners.

Mounted on the primary drive shaft 35 below the rst pinion 43 is a second pinion 45, said second pinion being vertically reciprocable on the primary drive shaft 35 and having formed integrally therewith upon the upper surface thereof a cylindrical boss 4l, said boss providing at its upper end an annular shoulder vi8 adapted to receive a clutch annulus 49 formed of brake material and adapted to act as a clutch against the under side of the first pinion 43. The second pinion 46 is supported for reciprocation on the imary drive shaft 35 by means of ball bearings Disposed beneath the second pinion is a lever 53, said lever providing a yoke 5d intermediate its ends. Pivotally suspended in the yoke 54 is a sliding collar 55 which is reciprocable 4 on the primary drive shaft 35 and has its upper end engaging the lowermost of the ball bearings 5I on which the second pinion 45 is mounted. One of the ends of the lever 53 is pivotally secured to the upper end of the armature 5l of a solenoid 58 while there is secured to its opposite end a brake pad 60 which constitutes a brake 6i for a purpose which will be described in greater ldetail below.

Disposed below the yoke 54 of the lever 53 is a compression spring 63, said spring having its upper end seated upon the under side of the collar 55 and its lower end seated upon the upper wall 26 ofthe .enclosure 25 adjacent the 4bearing Thus, it can Lbe seen that the compression spring 6.3 `biases the sliding .collar 5.5 upwardly -on the primary drive shaft 35 causing the .concomitant upward movement of the second pinion 46 and the engagement of the clutch annulus A8 lwith `the underside of "the rst pinion '43 to establish driving connection between the first pinion andthe second pinion '46 so that the second pinion it may he driven thereby. How- :f

even'when the solenoid 58 is energized, in a manner to be described in greater detail below, the armature 5:1 thereof is drawn downwardly to draw the end of the lever .53 piero/tally .con-

nected thereto .downwardly and. to 'urge Athe 5 sliding collar 5.5 mounted iin `the yoke 54 down- -wardly against the bias of the coznpresson spring B3, permitting the second pinion 4B to slide downwardly `on the primary .drive :shaft 35 and disengaging the clutch annulus "49 trom the under side of the first zpinion 43 :to break the ng connection between the first pin-ion 43 and the second pinion 45.

Positioned centrally of the chamber 23 and .constituting a portion ofthe first secondary drive is a rst secondary drive shaft 65 YWhose upper and lower ends are mounted, respectively, in bearings 65 and 51 which, in turn, are mounted, respectively, in an upper, transverse partition 69 and in the upper -wall 26 of the enclosure 25. Aixed to the first secondary drive shaft 65 adjacent its lower end is a rst spur gear which is in mesh with the second pinion 46 on the primary drive shaft 35. Supported `upon the rst secondary drive shaft 65 is a second seconf dary drive shaft 1I which encompasses the rst secondary drive shaft 65 and has its upper and lower ends terminating, respectively, at points substantially below .and Aabove the upper and lower ends of the hrst secondary drive shaft 65. Secured to the second secondary drive shaft 1| at the lowermost end thereof is a second spur gear 73 which is-in -mesh with the first pinion 43 Amounted Von the Drimary'drve shaft 35. A third, secondary drive shaft encompasses a portion ofthe second secondary drive shaft 1I and 'has .secured to .its lowerrnost end a Vthird spur gear 11, it Abeing noted that -the first and third spur .gears ic and 11 constitute the lower :and upper gears while the second spur gear :13 constitutes the intermediate spur Spaced from but having its longitudinal axis oriented substantially in parallelism with the secondary drive shafts 65, 1| and 15,is a countershaft 8c the upper and lower ends of said shaft being journaled, respectively, in bearings 8| and 82, supported, respectively, in the intermediate partition 24 and in the upper Wall 2.6 of the enclosure 25. Mounted on the countershaft 80 for rotation therewith is a counter pinion 84, said pinion 84 being in mesh With the first spur gear 10 so that the rotation of the spur gear 1|] is communicated to the counter pinion 84 Yand then to the countershaft 80. Fixed on the countershaft 8f3 adjacent the upper end thereof is a second counter pinion 85 which is maintained in mesh with the third spur gear 11.

Secured to the first secondary drive shaft $5 adjacent the upper end thereof is a first rotatable member 538 of substantially cylindrical configuration which has a transverse mounting web 89 upon which is provided a peripheral, vertical hangs V90 adapted to bear a circular scale providing indicia, not shown. Secured to the uppermost end of the second secondary drive shaft 1I lsniseccnd rotatable :member 92 which includes a 'mounting web 193 having .a vertical ange 94 provided V.tlnareupon lwhich provides a mounting .for 1a scale 95 'shearing indicia indicated generally at 36 lr). vliastened to the uppermost end .of ithe third secondary shaft 15 is a third rotatable .member y98 which includes a mounting 4web SSprovided vwith a peripheral, vertical flange |f00 upon which is supported a scale I0! having indicia VI|.|2 thereupon. Although only the C and Escales, as best shown in Fig. 1 of the drawings, are 'represented for purposes of convenience, it should -be lunderstood that it is intended to provide the conventional scales customarily incorporated Ain slide rules von the flanges 90, 94 and '|00 of the lfirst, second and third members 8B, 92 and :98.

'Ihe `electrical circuit of the slide rule le is shown in Fig. -5 of the drawings Land includes power input leads |04 and |05, the power input `lead |05 having a main switch IUE therein which "is controlled by aswitch'lever i t? mounted inthe Wall '|15 ofthe first housing l2. Tapped into the power leads `|04 and |05 are leads |539 and Ht which conduct current to lamps l and ||2 juxtaposed 'to the viewing opening IG in the wall |5 ofthe first 'housing I2 to illuminate the scales on the rotatable members 88, V92 and Q8. The leads |04 yand |05 are connected to a transformer |14, the secondary of which is connected to leads Y|16 'and I I1. Connected in series in. the lead I Il' lis a selenium rectifier IIS, a choke coil |20 being connected in the lead IIB between condensers |2I arranged in parallel between the leads IIS and 'I I"|. The solenoid 58 is connected to the lead H6 by means of a lead |23 and to the lead I|'| by means of a lead |24, a switch |25 being interposed between the lead |I'| and the lead |24.

The motor 28 is -of the reversing type and is connected to thev end of the lead I l5 at |21. The energization of the motor is controlled by a dual segment yswitch v|29 and Va dual segment rheostat |30, the dual segment switch |29 having a wiper arm I 32 which is connected to the motor 28 by means of a lead |33, its left-hand segment being connected to the motor through a lead It! while its right-hand segment is connected to the motor Y2,3 through 'a lead |35 which taps into a lead |35. A wiper arm |31 of the rheostat is connected to .the end of the lead II1, its left-hand segment being connected to the end of the lead |35 while its right-hand segment is connected by a lead |38 which is tapped into the lead |34 to the motor 28.

The second control housing l is substantially square in coniigurat-ion and is connected to the lirst scale containing housing by means of a flexible conductor |38. The housing i3 provides a chamber |49 in which are disposed the solenoid control switch |25 which constitutes the second control means, and the motor control switch |25 and the rheostat |33 which constitute the Erst control means. It will he noted that the solenoid switch |25 is controlled by a lever l mounted on a switch shaft M2 while the movement of the wiper arms |32 Vand I 31 of the motor switch iid and rheostat |30, respectively, is controlled by a lever |43 mounted on a shaft ldd which is common to both of the wiper arms |532 and |32. Thus, the movement of the lever lf' will cause the concomitant movement of the switch and wiper arms |32 and |31 in the same direction at the same time.

When it is desired to .cause the simultaneous rotation of the rotatable members t8, 62 ands,

the lever |43 is depressed in the appropriate direction to cause the wiper arms E32 and |31 of the motor switch i2@ and the rheostat |30, respectively, to be carried to either the right-hand or left-hand segments thereof to cause the motor to be energized to rotate the members 88, 92 and 93 in either a clockwise or counterclockwise direction. When the motor 28 is so energized, the shaft 3| is rotated to cause the concomitant rotation of the pulleys 33 and it through the belt 4| and causing also the rotation of the first pinion 43. Since the solenoid 53 has not been energized, the compression spring 63 maintains the second pinion 56 at the upward limit of its movement so that the annular clutch 49 is maintained in continual contact with the under side of the first pinion 43, thus establishing a driving relationship between the first pinion Q3 and the second pinion Lit. Therefore, when the primary drive shaft 35 is rotated by the energization of the motor 28, the iirst pinion i3 causes the rotation oi the second or intermediate spur gear 'i3 while the second pinion dit, being operatively connected to the under side oi the first pinion 43 by means of the clutch annulus 49, is driven thereby to cause the concomitant rotation of the iirst spur gear 1%. When the spur gear l@ is so rotated, it causes the concomitant rotation of the counter` pinion 8d which, in turn, rotates the countershaft Sil and the counter pinion 8b mounted upon the upper end there-of to cause the concomitant rotation of the third, uppermost spur gear 11.

Although the iirst control has been described as including the switch and rheostat |23 and ist, to control the energization or the motor 28 it is conceivable that other forms of control and motors might be utilized, such as two Selsyn motors substituted for the first control means and the motor 28.

When the iirst, second and third spur gears B, 13 and are thus rotated, the first, second and third rotatable members B3, 92 and 93 connected thereto are rotated in unison at the same speed and in the same direction, it being understood .f

that the direction of movement can be altered by the appropriate shifting of the lever M3 mounted on the control housing |3. It should also be noted here that, although the rotatable members t3, 92 and G8 are shown in superimposed relationship with the shafts 65, 'il and 'i5 maintained with their axes oriented in a vertical direction, it is conceivable that the axes of the secondary shafts be oriented in a horizontal direction and the rotatable members 88, $32 and 98 be placed in side-by-sicle rather than in superimposed relationship, ii such orientation is desirable.

1n order that the rotatable members tit, 92 and 98 may be differentially rotated, the solenoid 5B is energized through the actuation of the solenoid switch i by means of the lever ili mounted on the control box i3, said energization of the solenoid 53 causing the downward movement of the armature 51 and urging the collar 55 downwardly against the bias of the compression spring G3 to permit the second pinion d5 to drop downwardly and carry the clutch annulus da away from engagement with the under side of the nrst pinion 43 thus breaking the driving engagement between the iirst and second pinions @it and 46.

Simultaneously, the brake 6| on the opposite end or the lever 53 is carried upwardly against the under side oi the iirst spur gear 'i0 to prevent the inadvertent rotation of the first and third spur gears 'HJ and T1, respectively, since, when the movement of the iirst spur gear 10 is retarded the third spur gear 11 is prevented from moving by the driving-driven relationship established between these gears through the countershaft 3d. Therefore, while the first and third spur gears 'm and '|1 are restrained against movement, the second, intermediate spur gear 'I3 is rotated by means of the iirst pinion d3 to a desired position. Subsequently, after the movement oi the intermediate spur gear 13 and its associated rotatable member 92 has been accomplished, the solenoid 5B is de-energized by appropriate movement of the control lever I4! to permit the concomitant rotation of the members 88, 92 and 98 in the desired direction.

In order to illustrate the manner in which the slide rule li! can be utilized in solving slide rule problems, the C and D scales of the slide rule have been represented in Figs. 7, 8 and l of the drawings in the positions which they assume during the solution of a simple problem. To solve the problem 2X3, it is necessary to rotate all of the rotatable members simultaneously so that the numeral 2 on the D scale is visible through the viewing opening l5, as best shown in Fig. 7 of the drawings. Subsequently, as best shown in Fig. 8, the intermediate scale 95 is rotated, as previously disclosed and described, to bring the index on the C scale opposite the numeral 2 on the D scale. All of the scales are then simultaneously rotated until the numeral 3 of the C scale is at the reference line i9. The answer 6 may then be read on the D scale.

Another example, not illustrated inthe drawings, of the solution of a more complex problem involving the ascertainment of the answer to the fraction non 1.5X8

involves the following steps:

All of the scales are rotated simultaneously so that 2 on the D scale is visible. The second rotatable member 92 is then rotated diierentially with respect to the first and third rotatable members 33 and 98, respectively, to bring the index on the C scale opposite the numeral 2 on the D scale. Subsequently, all three of the rotatable members are simultaneously rotated so that the numeral 3 on the C scale is positioned at the reference line i9. The second rotatable member 92 is then diierentially rotated with respect to the other scales which are held against rotation so that the numeral l5 on the C scale is brought under the reference line SS. All of the scales are then rotated in a counterclockwise direction until the numeral 5 on the C scale is registered with the line i9. The second rotatable member S52 is then rotated until the numeral 3 on the C scale is registered with the line i9 and then all of the scales are rotated until the index of the C scale is registered with the line |9. The answer, 2.5, can then be read on the D scale opposite the index on the C scale.

I thus provide by my invention a slide rule which is controllable from a remote point by only one hand of the user so that computations may be written down without releasing the slide rule control. Furthermore, my invention permits involved calculations to be made more quickly than with conventional slide rules since the scales thereof are readily rotatable with reference to one another and can be quickly rotated to obtain the desirable results once the mode of actuation J of the slide rule is mastered. Because of the circumferential length of the scales, greater accuracy is obtainable. For instance, eight-inch diameter scales would yield greater accuracy than a twenty-four inch long conventional slide rule.

I claim as my invention:

1. In a slide rule, the combination of: a. housing; a plurality of differentially rotatable, cylindrical members mounted in said housing, said members bearing indicia upon the peripheral portions thereof; a motor in driving engagement with said members for rotating said brake means for releasing at least one of said members from driving engagement with said motor and preventing rotation of said member with reference to others of said members; a first remote control for energizing said motor to simuld taneously rotate said members; and a second remote control for energizing said brake means to prevent rotation of said member with reference to others of said members.

2. In a slide rule, the combination of: a cylindrical housing providing a viewing Window in the side wall thereof and having a reference line eX- tending vertically across said window; a plurality of cylindrical members mounted in said housing concentrically therewith and diiferentially rotatable with respect to said reference line, said members bearing upon their peripheral portions vertically oriented indicia perceptible through said window; a motor for rotating said members; means for preventing rotation of at least one of said members with reference to others of said members; a first remote control for energizing said motor to simultaneously rotate said members; and a second remote control for energizing said means to prevent rotation of said member with reference to others of said members.

3. In a remotely actuable slide rule, the coinbination of: a housing providing a viewing opening and having a reference point thereupon; a plurality of members mounted in said housing and differentially rotatable with respect to said reference point, said members bearing ori-their peripheral portions scales perceptible through said viewing opening; a reversible motor in said housing operatively connected to said members for rotating said members in either direction; brake means for releasing at least one of said members from operative engagement With said motor and preventing rotation of said member with reference to others of said members; a remotely positioned housing operatively ecnnected to said rst housing; a rst control in said remotely positioned housing for energizing said motor for simultaneously rotating said members; and a second control in said remotely positioned housing for energizing said brake means to prevent rotation of at least one of said members with reference to others of said members.

4. In a slide rule, the combination of: a housing; a motor in said housing; a plurality of scales mounted for differential rotation in said housing; a plurality of drives operatively connecting said motor and said scales, said drives including a primary drive and a plurality of secondary drives mounting said scales, and said primary drive being continually and operatively connected to at least one of said secondary drives to cause the differential rotation of at least one of said scales with respect to others of said scales, the others of said secondary drives being operatively connectible to said primary drive to cause the conlil comitant rotation of all of said scales; electromagnetic means for throwing said primary drive into operative connection with said others of said secondary drives; and a first control for energizing said motor to actuate said drives for simultaneously rotating said scales.

5. In a slide rule, the combination of: a housing; a motor in said housing; a plurality of scales mounted for differential rotation in said housing; a plurality of drives operatively connecting said motor and said scales, said drives including a primary drive and a plurality of secondary drives mounting said scales and said primary drive being continually and operatively connected to at least one of said ysecondary drives to cause the differential rotation of at least one of said scales with respect to others of said scales, the others of said secondary drives being operatively connectible to aid primary drive to cause the concomitant rotation of all of said scales; a brake for preventing the rotation of the others of said secondary drives when not operatively connected to said primary drive; electromagnetic means for actuating said brake; a first control for energizing said motor to actuate said drives for simultaneously rotating said scales; and a second control for energizing said electromagnetic means to brake the others of said secondary drives While said one drive is actuated.

6. In a slide rule, the combination of: a housing; a motor in said housing; a primary drive shaft operatively connected with said motor; a first secondary drive shaft operatively connectable to said primary drive shaft; a second secondary drive shaft encompassing a portion of said rst secondary drive shaft and operably connected to said primary drive shaft; a third secondary drive shaft encompassing a portion of said secondary drive shaft, said third secondary drive shaft being operatively connected with said first secondary drive shaft; a scale carried by each of said secondary drive shafts and rotatable therewith; and means within said housing for operatively connecting and disconnecting said rst secondary drive shaft to said primary drive shaft.

7. A slide rule as claimed in claim 6 in which said housing is cylindrical and said secondary drive shafts extend axially within said housing.

8. A slide rule as claimed in claim 6 in which said means for operatively disconnecting said first secondary drive shaft from said primary drive shaft includes a lever carried by said primary drive shaft, a retractable armature pivotally connected to one end of said lever, and electromagnetic actuating means for retracting said armature.

9. A slide rule as claimed in claim 7 in which said scales are cylindrical and are rotatable Within said housing.

10. A slide rule as claimed in claim 8 including control means without said housing for energizing said electromagnetic actuating means.

PAUL J. TOIEN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 443,772 Kells Dec. 30, 1890 513,213 Stanton Jan. 23, 1894 1,083,597 Cummings Jan. 6, 1914 2,080,857 Baer May 18, 1937 2,134,901 Wey Nov. 1, 1938 2,285,774 Horner June 9, 1942 2,527,776 Taafe Oct. 31, 1950 

